This is a minimal reproducer for a bug in bootsnap, or at least a behavior difference vs vanilla MRI.
To reproduce, compare output between:
$ bundle exec ruby require.rb
and
$ env BOOTSNAP_CACHE_DIR=$(pwd)/cache bundle exec ruby require.rb
You will see that the first run never requires a/file.rb, and
returns false on the second require call, whereas the second
invocation requires both files.